Poon Art, Chao Lin
Division of Biology, University of California, San Diego, California 92093, USA.
Genetics. 2004 Jan;166(1):19-24. doi: 10.1534/genetics.166.1.19.
The pervasiveness of sex and recombination remains one of the most enigmatic problems in evolutionary biology. According to many theoretical models, recombination can increase the rate of adaptation by restoring genetic variation. However, the potential for genetic drift to generate conditions that produce this outcome has yet to be studied experimentally. We have designed and performed an experiment that reveals the effects of drift on existing genetic variation by minimizing the influence of variation on beneficial mutation rate. Our experiment was conducted in populations of RNA bacteriophage Phi6 initiated from a common source population at varying bottleneck sizes. The segmented genome of this virus results in genetic exchange between viruses that co-infect the same host cell. In response to selection for growth in a high-temperature environment, sexual lines outperformed their asexual counterparts on average. The advantage of sex attenuated with increasing effective population size, implying that the rate of adaptation was limited by clonal interference among segments caused by drift. This is the first empirical evidence that the advantage of sex during adaptation increases with the intensity of drift.
性和重组的普遍性仍然是进化生物学中最神秘的问题之一。根据许多理论模型，重组可以通过恢复遗传变异来提高适应率。然而，遗传漂变产生导致这一结果条件的可能性尚未通过实验进行研究。我们设计并进行了一项实验，通过最小化变异对有益突变率的影响来揭示漂变对现有遗传变异的影响。我们的实验是在从一个共同源种群开始的不同瓶颈大小的RNA噬菌体Phi6种群中进行的。这种病毒的分段基因组导致共同感染同一宿主细胞的病毒之间发生基因交换。在高温环境下生长的选择压力下，有性系平均表现优于无性系。随着有效种群大小的增加，性的优势减弱，这意味着适应率受到由漂变引起的片段间克隆干扰的限制。这是第一个关于适应过程中性的优势随着漂变强度增加的实证证据。
